Remote-control devices are already known which consist of a portable transmitter and a receiver connected to the object to be controlled. Control can be carried out by means of infrared rays, the transmitter emitting a signal which has to be received by the receiver so as to trigger a function, for example unlocking.
In the case of a residence door, the receiver is accessible from outside and is therefore vulnerable. Moreover, an orifice for accommodating the receiver has to be provided in the door.